Unsaturated flow entails complex interactions of widely diverse materials—minerals, air, water in all its phases, living organisms with their products and remnants, and chemicals, both natural and anthropogenic. Many of these processes are poorly understood. Consequently, the generally accepted theory of unsaturated-zone flow routinely fails to predict adequately. Our project aims to develop quantitative generalizations and techniques that are widely applicable, closely tied to the critical issues we need to address, and closely representative of observed phenomena.
Nimmo, J.R., 2007, Simple Predictions of Maximum Transport Rate in Unsaturated Soil and Rock: Water Resources Research, v. 43, no. 5. (PDF).
Nimmo, J.R., 2010, Theory for Source-Responsive and Free-Surface Film Modeling of Unsaturated Flow: Vadose Zone Journal, v. 9, no. 2, p. 295–306. (PDF).
Nimmo, J.R., Mitchell, L., 2013, Predicting vertically nonsequential wetting patterns with a source-responsive model: Vadose Zone Journal, v. 12, no. 4. (PDF).
Mirus, B.B., and Nimmo, J.R., 2013, Balancing practicality and hydrologic realism--A parsimonious approach for simulating rapid groundwater recharge via unsaturated-zone preferential flow: Water Resources Research, v. 49, no. 3, 2012WR012130, doi: 10.1002/wrcr.20141, p. 1458–1465. (PDF).
Ebel, B.A., and Nimmo, J.R., 2013, An alternative process model of preferential contaminant travel times in the unsaturated zone--Application to Rainier Mesa and Shoshone Mountain, Nevada: Environmental Modeling and Assessment, v. 18, no. 3, doi: 10.1007/s10666-012-9349-8, p. 345-363. (PDF).
Cuthbert, M.O., Mackay, R., and Nimmo, J.R., 2013, Linking soil moisture balance and source-responsive models to estimate diffuse and preferential components of groundwater recharge: Hydrology and Earth System Sciences, v. 17, no. 3, doi: 10.5194/hess-17-1003-2013, p. 1003-1019. (PDF).
Su, G.W., Nimmo, J.R., and Dragila, M.I., 2003, Effect of isolated fractures on accelerated flow in unsaturated porous rock: Water Resources Research, v. 39, no. 12. (PDF).
Nimmo, J.R., and Malek-Mohammadi, S., 2015, Quantifying Water Flow and Retention in an Unsaturated Fracture-Facial Domain, in Faybishenko, B., Benson, S.M., and Gale, J.E., eds., Dynamics of Fluids and Transport in Fractured Porous Systems, Geophysical Monograph 210, AGU (Wiley), p. 169-179. (PDF).
Nimmo, J. R., 1991, Comment on the treatment of residual water content in "A consistent set of parametric models for the two-phase flow of immiscible fluids in the subsurface" by L. Luckner et al.: Water Resources Research, v. 27, p. 661-662. (PDF).
Rossi, C., and Nimmo, J. R., 1994, Modeling of soil water retention from saturation to oven dryness: Water Resources Research, v.30, p. 701-708. (PDF).
Nimmo, J.R., Herkelrath, W.N., Laguna Luna, A.M., 2007, Physically Based Estimation of Soil Water Retention from Textural Data: General Framework, New Models, and Streamlined Existing Models: Vadose Zone Journal 6:766-773. (PDF).
Nimmo, J. R. and Akstin, K. C., 1988, Hydraulic conductivity of a saturated soil at low water content after compaction by various methods: Soil Science Society of America Journal, v. 52, p. 303-310. (PDF).
Nimmo, J. R., 1992, Semiempirical model of soil water hysteresis: Soil Science Society of America Journal, v. 56, p. 1723-173. (PDF).
Nimmo, J. R., Rubin, J., and Hammermeister, D. P., 1987, Unsaturated flow in a centrifugal field: measurement of hydraulic conductivity and testing of Darcy's law: Water Resources Research, v. 23, p. 124-134. (PDF).
Nimmo, J. R., 1990, Experimental testing of transient unsaturated flow theory at low water content in a centrifugal field: Water Resources Research, v. 26, p. 1951-1960. (PDF).
Nimmo, J.R., 2005, Unsaturated Zone Flow Processes, in Anderson, M.G., and Bear, J., eds., Encyclopedia of Hydrological Sciences: Chichester, UK, Wiley, p. 2299-2322. (PDF).
Nimmo, J.R., 2009, Vadose Water, in Likens, G.E., ed., Encyclopedia of Inland Waters: Oxford, UK, Elsevier, v. 1, p. 766-777. (PDF).
Nimmo, J.R., 2013a, Porosity and Pore Size Distribution, Reference Module in Earth Systems and Environmental Sciences, Elsevier, doi: 10.1016/B978-0-12-409548-9.05265-9. (PDF).
Nimmo, J.R., 2013b, Aggregation--Physical Aspects, Reference Module in Earth Systems and Environmental Sciences, Elsevier, doi: 10.1016/B978-0-12-409548-9.05087-9. (PDF).
Nimmo, J.R., 2015, Preferential Flow—Stokes Approach to Infiltration and Drainage [Book review]: Vadose Zone Journal, v. 14, no. 7, doi:10.2136/vzj2013.03.0054. (PDF).
Landa, E.R., and Nimmo, J.R., 2003, The life and scientific contributions of Lyman J. Briggs: Soil Science Society of America Journal, v. 67, no. 3, p. 681-693, cover, i. (PDF).
Nimmo, J.R., and Landa, E.R., 2005, The soil-physics contributions of Edgar Buckingham: Soil Science Society of America Journal, v. 69, no. 2, p. 328-342. (PDF).
Nimmo, J.R., 2008, The Public Fountains of the City of Dijon by H. Darcy--translated by P. Bobeck [Book Review]: Vadose Zone Journal, v. 7, no. 4, p. 1311-1312. (PDF).
In 2016 and later:
Develop a self-consistent model of hydraulic properties that control the transfer of water and dissolved substances between preferential flow channels and the surrounding matrix material, as needed especially in contaminant transport problems.
Evaluate the various possible physical modes of preferential flow, including filled and unfilled conduits, sliding drops, rivulets, and films. Apply hydrodynamic theory to develop appropriate mathematical representations for them in a subsurface flow model.
Conduct lab experiments to evaluate the possibility of thresholds in water content or applied flux at which preferential flow begins to be generated, a major issue with respect to predicting when preferential flow does and does not occur.